This invention relates to gas generators in general and more particularly to a method for starting up a gas generator for the catalytic reaction of hydrocarbons with an oxygen containing gas to form a fuel gas and for starting up an internal combustion engine which is to be supplied with the fuel gas, wherein catalytic material is temporarily electrically heated in a reaction chamber containing a catalytic charge; a mixture of hydrocarbons and air, richer in oxygen than the mixture used in continuous operation, is conducted over the catalytic material, is reacted there exothermically for further heating of the catalytic charge, and the fuel gas produced is fed to the internal combustion engine; as well as apparatus for implementing this method.
Gas generators can be used, for instance, to catalytically convert hydrocarbon containing fuels into a fuel gas which is better suited for the operation of internal combustion engines than liquid fuel. For, in internal combustion engines supplied with liquid fuel, for instance, in motor vehicles, the incomplete evaporation of the fuel and the uneven mixing with combustion air lead to incomplete combustion and emission of harmful substances. In addition, antiknock agents must as a rule be admixed to the fuel causing the content of substances in the exhaust gas which are harmful to the health to be increased further. The hazardous pollution of the air can largely be prevented if the internal combustion engine is operated with fuel gas. This fuel gas can be generated, as is described, for instance, in the U.S. Patent Application Ser. No. 633,609, in a reformed gas generator by partial catalytic oxidation of evaporated or vaporized liquid fuel with an oxygen containing gas, and the fuel gas then burned, together with additional combustion air, in the internal combustion engine. Since this fuel gas (reformed gas) has a high octane number, the addition of antiknock agents is not required.
A mixture of air and exhaust gas of the internal combustion engine, for instance, can be used as the oxygen containing gas for the reaction where the reaction is endothermic if the exhaust gas content is high and exothermic if the air content is high. To carry out the reaction, the catalyst must have an operating temperature which is above the start up temperature of the catalyst, the start up temperature of a catalyst being understood, as usual, to be that temperature at which the effect of the catalyst leads to a noticeable reaction. The operating temperature can be maintained by supplying heat to the generator from the outside, for instance, through an exchange with the hot exhaust gases of the internal combustion engine or by a supplemental electric heater. However, the temperature of the catalyst can also be controlled by changing the composition of the oxygen containing gas, i.e., the air/exhaust gas mixture, and by changing the thermal balance of the reaction accordingly. Thus, a compensation of the heat losses of the generator can be achieved by a light exothermic reaction.
In one known device a combustion chamber with a flame ignition plug is arranged at the entrance of the reaction chamber. In the combustion chamber a gasoline/air mixture is ignited simultaneously with the starting of the internal combustion engine connected to the reformed gas generator. The flaming combustion of the gasoline produces hot flame gases which are drawn by the internal combustion engine through the reaction chamber together with a further reaction mixture of gasoline and combustion air. These gases heat the catalytic charge contained therein up to the start up temperature of the catalyst. From then on, the reaction mixture in the reformed gas generator itself is reacted and the flame is extinguished.
In U.S. Pat. No. 3,954,423 and in U.S. Application Ser. No. 633,609, further starting devices which precede the inlet to the reaction chamber of the reformed gas generator, which consist of a starting generator with a separate starting catalyst of small volume are described. Upon starting the internal combustion engine, a gasoline/air mixture is also ignited in the starting generator. The hot flame gases of the latter are drawn by the internal combustion engine through the starting catalyst and heat the latter up quickly. Then, a gasoline/air mixture is fed to the starting catalyst and is converted there into a hot fuel gas which in turn is drawn, for heating up the catalytic charge of the reformed gas generator, through the reaction chamber of the latter. At the same time, the flame is extinguished. This generates a fuel gas with which the internal combustion engine can be operated without load, shortly after the internal combustion engine is started, even before the reformed gas generator itself is heated up to the operating temperature. However, the starting generator, which precedes the inlet to the reaction chamber, requires additional space of its own, although such space is relatively small.
In U.S. Pat. No. 3,915,125, a starting procedure is described which makes use of an electric starting device which is arranged in the interior of the reaction chamber and precedes at least part of the catalyst in the flow direction. This starting device may consist, for instance, of incandescent electric wires which are coated with catalytic material and are connected into an external circuit. To start the generator, the internal combustion engine is driven, for instance, by an electric starter, the external circuit is closed and a slightly understoichiometric hydrocarbon/air mixture is ignited at the incandescent wires. The strongly exothermic reaction initiated thereby, which may take place with a flame or will at least have a tendency to an ignition, allows hot gases to be produced which heat the catalytic charge to above the start up temperature of the catalyst. The reaction of the hydrocarbon/air mixture can also be initiated at an electric starting device which consists of an electric heater resistor of catalytic material. This heater resistor is heated by an external circuit until the catalytic charge is heated above the start up temperature of the catalyst. At the same time, with the further heating of the catalytic charge the throughput of hydrocarbons is increased step by step and the air supply is throttled until the catalyst is heated to a reaction temperature suited for continuous operation and the transition to continuous operation can be made.
In all known devices and starting methods, the hydrocarbon fuel is overstoichiometrically or slightly understoichiometrically reacted with air during starting, so that a short starting time of the gas generator is achieved through violent development of heat and the internal combustion engine, which is to be operated with the fuel gas produced, can be put in operation quickly. It is a disadvantage in such operation that, with this relatively large supply of air, in the flame gases and at the catalyst initiating the reaction, temperatures occur which may lead to damage of the temperature sensitive catalysts. In the interest of greater safety, moreover, methods would be preferable, in which a flame reaction of the reaction mixture is avoided. In addition, a product gas is generated, at the beginning of the starting process, which has only a low calorific value and which must be drawn through the generator by the internal combustion engine in order to heat up the catalytic charge. However, to accomplish this, the internal combustion engine must first be kept running by an external energy source until the generator produces a gas with a calorific value sufficient to operate the internal combustion engine. In this last described prior art method, the vehicle's external energy source, e.g., the starter battery is simultaneously loaded by the start up heater and by the starter motor.